Dolby CP650 A/D (5.1) Conversion

[Joseph Re]

Good morning,
Happy New Year first of all

I am new here, and a colleague suggested I join to seek answers for a somewhat perplexing situation.
We (the AV company I rep) have a customer with a very large home theater. The primary setup is a very high-end JVC projector, various 4K BD players, streaming boxes, NAS, AudioControl X9s pre-amp and multiple Rotel power amps. The setup is 7.1.4. This is all controlled with Control4.

In addition, and this is the key part here, the customer has added two 35mm film projectors, related components, and a Dolby CP650 5.1 surround processor. When the DB25/XLR cable connection is made from the CP650 directly to the XLR ins of the Rotel amps, it all works perfectly. However, the existing connections from the AudioControl X9s have to be physically disconnected from the amps - this is clearly NOT ideal. The obvious trick here is the need to convert the output channels from the Dolby processor into something that the X9 can process (digital toslink?) and send those signals to the corresponding speaker channels.

Failing that, maybe adding another amp/amps with XLR ins and splitting the speaker connections with some type of junction/splitter (whether manually switched or controllable). Not sure I am a fan of this approach but I am grasping a bit here. Just a note, I can get 2-channel into the X9s no problem because it has an XLR pair for CD input. This is of course not acceptable for the client.

Finally, I have spoken to Dolby, and their position is that this unit is so old this configuration is unsupported. I also had a call with Lynx to discuss the Aurora(n) product, but it's the 'real-time' Dolby encoding that will likely be the sticking point in any of these configurations.

To summarize and note, we are not trying to achieve ATMOS or 7.x.x encoding, simply getting the 5.x audio from the Dolby processor to the speakers without disrupting the existing configuration.

I appreciate you reading this far, and any insights or ideas would be greatly appreciated. Thank you.
Kind Regards
- Joe

[Tony Bandiera Jr]

Your three best options would be:

1. Have someone build you a custom relay based switch box supporting all six channels, using gold contact miniature relays. Supply a contact closure for film mode, the outputs from the CP650 would enter the Normally Open contacts on the relays. The Normally closed contacts would route the audio from your A/V sources. I used to build just such a device for some installs I did many years ago.
2. Use three stereo mixers with two or more inputs on each mixer. Install between the CP650, X9, and the power amps inputs. Set mixers for proper gain (ideally unity) from each source. No switching would be required. The only penalty would be be an increase in hiss (noise floor) which would depend on the quality of the mixers used.
3. Best option: Replace the X9 with a unit that has enough inputs (including an analog 5.1 input set) and reprogram the control system. It will give the best overall performance.

A fourth option, and the one I used in all of my screening room installs, is to use the CP650 as the "master" pre-amp, where the outputs of all the alternate content (DVD, etc,) went to the analog input on the CP650 and the CP 650 selected that input for all alt content and the preamp controlled to sources. your signal path looked like this:

(Sources) - X9(pre-amp) - CP650 - Amps - Speakers.

The CP650 did EQ and Volume (level) controls for everything. The pre-amp (in my case, a Denon AVR) selected sources, provided level trims as needed, at a preset volume level that my AMX (or Crestron) would automatically call upon power up or source changes. The output then went to the CP 650, where the CP650 fader did the actual room volume changes.


I strongly advise against switching speaker outputs..you will need reliable high current relays or sealed switches, and ANY cross connections or shorts caused by the switching WILL damage amplifiers! (And some amplifiers will not tolerate even momentary open or short circuits on the speaker outputs.)

For options 2 and 3, it is very important to make sure that the Dolby Processor levels are set to reference (7.0 on the Dolby fader) and the default level on the X9, mixers, or other preamp to get the correct balance and SPLs from the system. As for EQ, if the preamp provides EQ for the system, set the EQ in the CP 650 to flat in most of the bands, but use the CP 650 EQ to roll off the high end as per the cinema EQ curve. (You generally don't want to do full range EQ on top of full range EQ.)

Reach out to me via the messages on the forum if you need further help.

[Stefan Scholz]

Seems to be typical for home installations, that these rely mostly on their components that are from the home market.
Beside 2 ch analog audio, there is no need for analog multichannel inputs or AES 3 signal inputs other than 2 ch SPDIF/ TOSLINJK..
The CP 650 is a legacy hardware going back many years, and reaching 25 years since introduction. So it is an image of the cinema technology of the time.
Meaning, requirement for 6 channel analog input, 2 channel analog input, low level photocell 2 channel input and 6/ 8 channel balanced analog outputs to directly feed a loudspeaker system.
The good thing was, it could be expanded. For studio usage an AES 3 input/ output card could be installed, delivering digital interfacing, which is easier to convert into a modern digital based structure, than going the analog way with D/A A/D conversion.
The X9s just does, what todays home tech needs, a ton of high bandwith HDMI inputs with a switcher, sound deembedding and decoding, some 2ch unbalanced inputs, EQ and analog feeds towards power amps in balanced and unbalanced outs, wrapped in a fancy packaging at a home style price tag. Such equipment is not really that flexible outside its ecosystem.
As known, high end home theatre is also using DCP movie sources these days, and specific residential and home theatre projectors exist from all major vendors.
Some of these sites do still feature movie projection of 35 mm film, from the history of the collector.
This requires a different approach in high end home theatre, your control box must accept AES 3, AES 67, and analog multichannel. Plus HDMI input switching with sound deembedding.
Or a converter that converts the analog audio into HDMI. I am not really aware of possible units known to successfully do that task. I know, a solution that converted multichannel AES 3 and Video into HDMI existed at some point.
I am thinking of the Datasat AP 25 (20) audio processor sold for movie theatres (a fancy home version with stylish case and adjusted price tag to match the wallet of home enthusiasts exists, called RS 20i) did the purpose better, than the X9s box does. If is upgradable with a film input card, features 4 HDMI inputs with deembedding and audio decoding, 2 stereo analog RCA inputs, up to 16 channel digital AES in/ out, 16 ch analog out with active crossover option and an 8 ch balanced analog input, SPDIF RCA, Toslink x 2. And, it also supports the "magic" DIRAC live EQ, if requested. Controllable via VNC from the sofa, everything is there.
More or less the swiss knife for home theatre use. It does everything needed in one box, and comes with the required connectors.
This has normally been my solution for home setups. We were able to integrate a movie projector, digital DCI projector, UHD disk players, and stereo gear. Just to remind, the older version did only provide an HDMI 1.4 switch, the newer versions are 2.X compatible.

[Carsten Kurz]

I guess the 'easiest' would be an analog audio to HDMI embedder. They are not easy to source, though.

[Leo Enticknap]

Arvus used to make one, which I used on one install to get analog multi-channel audio into a CP950 via its HDMI input. But it wasn't cheap, and I can't find any mention of it on their website now.

Best option: Replace the X9 with a unit that has enough inputs (including an analog 5.1 input set) and reprogram the control system. It will give the best overall performance.

The only one I can think of off the top of my head is the JBL SDP-75, which (as Carsten notes on another thread) is hellish pricey. The Trinnov OV2 has a 5.1 analog input set, but no HDMI inputs, which pretty much rules it out for home theater applications.

[Joseph Re]

Thank you all for the responses! I will read through and see what makes the most sense and of course what hardware is available to even implement any of these solutions. Thanks again!

[Jim Cassedy]

The only issue I have with using HDMI embedders/de-embedders in situations like this is that
many of them will introduce a bit of a delay in the audio stream, which can throw lip-sync off.

[Joseph Re]

This customer is a well known artist and music producer, and when I tell you he can see and hear every single little blip or drop, it is no exaggeration.
Any kind of delay or drop out, even a millisecond, would be totally unacceptable.

I fixed a (nearly imperceptible) frame-drop issue with his video scaling system (Lumagen - with their technical help), by changing gen-lock settings in the scaler and syncing and locking all the video input settings, and making changes/upgrades to the HDMI cabling.
There is also a ton of custom programming in the C4 remote for screen masking, resolution changes and audio delay adjustments.
We took this over from another AV company that initially installed it but couldn't work out the bugs, apparently.

All of this Dolby film stuff is new additions (because he's a film buff "hobbyist"). Just trying to get him the experience he wants. Thank you.
Regards

[Leo Enticknap]

If this is a "money no object" deal, and to avoid disrupting the alternative content system, which you say has been tweaked to within an inch of its life and should not be disrupted further, then what about putting a Q-Sys core downstream from both the CP650 and the X9, and basically using it as a switcher between the two? I look after some Bel-Air Circuit rooms, the owners of whom want to retain film projection capability, and that's what we've done in one of them (except that the audio processor for alternative content is an SDP-75 rather than an X9). I have done other theater installs in which the entire audio and automation system is handled by Q-Sys, but with the master analog outs of a CP650 going into it, and the CP650 being used for film audio only.

[Joseph Re]

Maybe not "no object", but if it's the right solution he'd likely be willing to do it. I'd have to research the Q-Sys and how that might work, I am not at all familiar with the system and how it would integrate.
Thank you!

[Tony Bandiera Jr]

I spoke with Joe via message, and there is a tidbit that needs to be emphasised (I admit to missing it in the original post) this is a 7.1.4 system... so there are also "Atmos"/height channels in the installation at hand.(Evidently processed by the X9). I think that Leo's suggestion of Qsys is looking like the best option IMHO.

Having dealt with high profile and sharp high end clients myself, any option chosen must be robust, consistent, and not add any audible delay or artifacts to the sound. Which brings to mind..in this case, with a Qsys core handling the analog audio only, does it introduce any delay/latency? (or will it be used to handle digital outs from both the X9 and CP650?) I have not personally used Qsys, I "retired" before it was rolled out.

[Leo Enticknap]

I'm a bit hazy on this, but believe that the CP650 can output AES3 with the right card in it - just not input and output. Whichever you choose, the approach I'd take would likely be to set the global delay to zero on the CP650 and the X9, and then tweak individual input delays as needed within the Q-Sys design. You could also do the EQ/tuning in Q-Sys, leaving both input processors flat, meaning that you would only have to tune at one point in the signal chain.

Q-Sys would allow complete flexibility in terms of channel routing, too, so if our VIP wanted something wacky, like 35mm SR-D LFE playing through in-room bass management speakers, that could be done.

[Sam Chavez]

The 650 did indeed have a digital audio option. It is the Cat. 778. However there are none available. I gathered these from EU and and South America. and sold every one I could find and they're no more. This card was intended for dubbing application, so not a lot were ever built. I would bet when the 650 was removed from service no one bothered to save the 778.

[Sean McKinnon]

Joseph,

We are located in Boston and have extensive experience in both 35mm film projector installation and maintenance as well as integrating film into home screening rooms and with Q-Sys both in Cinema and non-cinema applications. Feel free to reach out on messenger if you want.

[Ioannis Syrogiannis]

If any delay is a result of the CP650 only, one should consider that the SR-D reader (x2, for two projectors) could move, to give some advantage.
After all, I remember SR-D (not DTS) readers being added before the head.
(First time I saw that, not knowing that it may be an option, my mind was blown. )